Electrical control system



July 8, 1947.

A. B. CHRISTENSEN ELECTRICAL CONTROL SYSTEM Filed 001:. 2, 1943 5 l2 9 A I v 3/21 52/ 2- I I 3/2 3 I 5/2 309 3/6 INVENT OR.

Patented July 8, 1947 ELECTRICAL CONTROL SYSTEM Andrew B. Christensen, Snyder. N. Y., assignor to The Rudolph Wurlitzer Company, Chicago,

Ill, a corporation Application October 2, 1943, Serial No. 504,713

9 Claims.

This invention relates to the electrical control of electric current responsive or operable apparatus.

The chief object of the invention is to provide an electrical control of predetermined character for electrical apparatus, etc., solely responsive to certain characteristics of the electrical energy applied for the operation thereof.

The chief feature of the invention resides in the provision of a control that supplies electrical energy to electric apparatus, the energy having predetermined characteristics such that any energy applied by tampering, etc., will fail to energize the apparatus.

The invention, accordingly, is directed to a safety control circuit such that the electrical apparatus, protected and controlled thereby, cannot be operated by accident or design, except at that time or under those conditions that are characteristic or inherent in the apparatus to be operated.

Specifically, the invention contemplates activation by differences of phase, different amounts of voltage, or both i. e. predetermined voltage being applied only when the control apparatus is lawfully or properly energized.

The invention is not necessarily singular in character, but may protect a plurality of devices as hereinafter set forth.

Many devices, such as motion picture machines, phonographs, organs, pianos, radios, public address systems, telephones, industrial and military signal systems, to mention but a few applications, are designed to be set in operation by the closing of a switch at a point remote from the device set in action. As at present designed, many such devices may be set in action illicitly by a person intending to cheat a vending machine, or summon guards to divert their protection from a point of attack, or start or stop a machine at a time when doing so would cause loss or damage. This is generally done by bridging or short-circuiting the conductors of the control apparatus between the control station and the device to be controlled. By this illicit action the potential difference between any two conductors is different from the proper voltage to operate the critically preadjusted apparatus, which proper voltage initiates or terminates operation of the device. The proper voltage can be applied only by the additive or subtractive operations of the circuits completed through the central switch. This invention makes illicit operation possible only by shunting this switch. As this switch readily may be protected against tampering, it becomes practically impossible to energize the circuits of the invention otherwise than legitimately.

Other objects and features of the invention will be set forth more fully hereinafter.

The full nature of the invention will be understood from the accompanying drawing and the following description and claims.

In the drawings:

Fig. 1 is a diagrammatic wiring diagram of the simplest embodiment of the invention.

Fig. 2 is a similar view of a slightly more compllcated embodiment.

Fig. 3 is a similar view of a multiple embodiment of the invention.

Fig. 4 is a view similar to Fig. 3 and of a modified multiple embodiment of the invention.

In Fig. 1 wherein the simplest form of the invention is diagrammatically illustrated, 4 indicates the primary of an input transformer and 5 the secondary thereof, An autotransformer includes portion 6 and portion 1. Line It] connects one end of secondary 5 to the remote end of portion 5, while line H connects the other end of secondary 5 to the junction of portions 6 and I.

The other end of portion 1 is connected by line [2 to an electrical device 9 operable at predetermined values. The line l4 also connects device 9 to line Hi. At the instant that the upper end of secondary 5 is positive with reference to its lower end, the upper end of autotransformer 6 will be positive with reference to its lower end, while at the same time the electrical energy in portion 1 will be out of phase with electrical energy in portion 6.

If it be assumed that the secondary 5 generates or applies A volts and device 9 requires 2A volts to operate, the following is observed: The potential difference between lines I0 and II will be A volts and this also exists between lines H and [2. The potential difference between lines I0 and I2, accordingly, will be 2A volts or sufiicient to operate device 9 when switch 8 in line I2 is closed. This is normal operation and device 9 will operate.

Now if by accident or illicit intention lines l0 and i i are bridged, same merely short circuits secondary 5 without any effect upon device 9. If lines l l and i2 are bridged only, the A volts from secondary will be applied to device 9. Since same requires 2A volts for operation, the voltage A applied is insufficient for operation of device 9.

Accordingly, only by shunting switch 8 or closing switch 8 can the proper voltage be applied to device 5. The foregoing assumes that switch 8 and autotransformer 6-'! are suitably and adequately protected against tampering or illicit access.

Device 9 may be, by way of example only, of any suitable character, such as any one of those initially mentioned herein. Whatever it may be, the

present invention only requires that it be preadjusted to operate at or near the voltage supplied to lines i and l 2 by the cooperation of secondary and autotransformer S and 1, or their equivalents.

In Fig. 2 there is illustrated a slightly more complicated form of the invention. Herein I04 indicates the primary of an input transformer having two secondaries m5 and H3. Line H5 connects the remote or lower end of secondary I I3 to line i l 5 near that lines connection to the lower end of secondary I35. Line [M from the device lBiJ herein connects to the upper or opposite end of secondary i 23 instead of line I I!) as in Fig. 1. Lines 9-! H and H2, autotransformer |0SIll'l and switch 22 8 are similar to the :primary numeral designated (corresponding) elements in Fig. 1.

As before, when the upper end of secondary #35 becomes positive with reference to its lower end, portions W6 and ii of the auto transformer attain the polarity of portions 6 and 7, see Fig. 1. Secondary H3 herein, being wound on the same core as secondary E35 reaches like polarities, but is connected to device H39 by line H5 so that its phase is opposite to that of secondary 85.

If it is assumed that device lcEl requires 2A volts for operation and secondary 25 produces A volts, 9. potential difference of A volts exists between upper and lower ends of portion i516 and also of portion I07. Vi hen switch I08 is closed in this instance, the secondary H3 supplies an electrical potential of A voltage which, with the A voltage supplied by portion H31, impresses current at 2A voltage upon device N39 for its operation.

Now, if accidentally or by illicit intent, lines I l2 and l 58 are bridged no operation of device 108 results because the current from secondary I55 is out of phase with the current from secondary H3 and the efiective voltage is zero. Bridging lines H6 and ill merely short circuits secondary i85 without operation. Bridging lines ill and H2 supplies an inadequatevoltage (i. e. A volts) to device 169 from'secondary l 53, hence the device E 89 is not operated.

Only closing switch l-GB or shunting thereof can secure actuation or operation of device I09 which may be of the character hereinbefore generally indicated. As previously set forth, switch 132 and autotransfornier HEB-4 readily may be protected against unauthorized access, etc. Hence, device E09 is protected and accidental or unauthorized operation thereof is prevented.

Reference will now be had to Fig. 3 wherein a multiple form of the invention is diagrammatically illustrated. Herein 254 is the primary of the input transformer, 255 one secondary thereof, 2l3 another secondary thereof and H6 at third secondary thereof. The autotransformer has portions and 20?, the upper end of the former being connected by line 2!!! to the upper end of secondary 265. The junction of portions 205-201 is connected by line 2H to the lower end of secondary 295. Devices 299 and 289A are each adjusted for operation at 2A volts.

Herein switch member 263 connects by line 2 l2 and branches 2l2a and 2|2b to devices 289 and 289A, respectively. Switch 2 38 is arranged to make no contact with either of contacts 220 and 22! or make contact with either one, but not both at the same time. Contact 220 connects to the lower end of portion 201. Contact 22! connects by line 223 to line 25-.

The lower end of secondary 213 is connected by line 215 to device 209. The upper end of secondary H6 is connected by line 21'! to device 205A. The lower end of said secondary is also connected to line 21 l by line 2 l8 and line 2l4 from the upper end of secondary 2 l 3 similarly connects to said line 21!.

If, as before, it is assumed that there is a voltage of value A in each of the several windings when switch 268 contacts contact 220, the voltage of secondary 2 l6 and portion 201 are additive making a total voltage of 2A necessary for device operation, that is device 209A. When switch 2&8 contacts contact 221 the voltage of secondary 285 plus the voltage of secondary 213 totals 2A volts or that necessary to operate device 209. Thus one or the other of the two devices can be energized, actuated or operated by the single switch member 208, which therefore is of selective character. Naturally, when neither contact is engaged by member 293 the common line 2|2 to both devices is open and neither can be operated.

There are again. three lines (herein 2l0, 2H

2E2) bridgeable two at a time with the following results: When lines 2m and 2H are bridged secondary 285 is short circulted as before. When lines 2H) and 212 are bridged, there is no effective voltage ap lied to device 209A and 2A volts is applied to device 2&3. Hence, partial protection here obtains. When lines 2!! and H2 are bridged, each of the devices will have current supplied thereto at A volts, which is insuiiicient for operation of either device 289 or 288A.

As above set forth, device 209 is only partially protected, while device 209A is fully protected against operation by accidental or premeditated short circuiting of conductors. A circuit of this character is desirable where several devices are necessary but only one is to be protected as where device 269A would constitute a pilot control for device 299. In. this type of pilot, or secondary, or remote control relationship between the devices it is obvious that full protection of such pilot device ZBSA would insure adequate protection of the master device 289 unless, of course, it were desired to reverse the relationship for special inter-control device operation. Expressed broadly, another way, the devices 209 and 209A may be interlocked, either electrically or mechanically, and so arranged that the fully protected device 289A would have to be in operative condition before the unprotected or partially protected device 25 9 could be set in operation,

In Fig. 4 a modified form of the foregoing Fig. 3 modification is illustrated. Hereinnumerals of the three hundred series indicate parts like or similar to those in Fig. 3 indicated by two hundred series numerals.

In Fig. 3 the single switch member 208 selectively contacts the contacts 220 and 22! in turn connected to the lower end of autotransforrner portion 281 and line 223 to lin 210, respectively, and line 252 from switch 298 branched to both devices. In Fig. 4 the devices 389 and 308A have independent supplies, that is switch 3050. contacts the contact 320 to close lines 3l2a-3l2 to device 3&9 from autotransformer portion 39?. while switch 308!) contacts the contact 32| to close independent line 3l2b' and 323 to device 359A.

In. a manner previously described, bridging the several lines 3H 3! 1, 312a and 3l2b, other than bridging equivalent to shunting switch 3mm or 3082), will not impose the critical voltage value,

the critical phase or both upon the device or devices so each is similarly protected against accidental or illicit intentional operation.

As is well known in the control art, the two switch members 308a and 3118b may be mechanically connected together for simultaneous operation of the preadjusted devices or the sequential operation thereof. These switches also may be so connected together as by looking out electrically or mechanically so that but one device only and not the other device can be operated at any time.

While the invention has been illustrated and described in great detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character.

The several modifications described herein as well as others which will readily suggest them.. selves to persons skilled in this art, all are considered to be within the broad scope of the invention, reference being had to the appended claims.

The invention claimed is:

1. An alternating current supply circuit for a device operable only at a preadjusted value, the circuit comprising an input transformer with secondary means, an autotransiormer, a portion of which is connected across said secondary means, a control switch in series with another portion of the autotransformer and connected to one terminal of th device, the other terminal of the device having connection to the secondary means, the device operating current having proper phase and being of a value bearing a definite multiple ratio to that of the secondary value and greater than the supply voltage from the secondary means to the autotransformer.

2. A circuit as defined by claim 1 wherein the secondary means includes multiple windings, the said other terminal of the device connecting to on of the secondary multiple windings other than the one that is connected across the first mentioned portion of the autotransformer.

3. A circuit as defined by claim 2 wherein a second device is operable at the same preadjusted value as the first device, said second device having one terminal in common with the first mentioned terminal of the first device, and its other terminal operatively connected to a third winding of the secondary means, said switch being arranged for selective connection to one of the connections between the autotransformer and th secondary means connected thereto and the said second mentioned portion of the autotransformer.

4. An alternating current supply circuit to a plurality of devices, each operable only at a common preadjusted value, the circuit comprisin an input transformer with a plurality of secondary windings, the number of secondary windings being one greater than the number of devices, an autotransformer having one portion connected across one of the secondary windings, each device having a terminal connected to an end of a secondary winding other than the autotransformer connected secondary winding, connections between the devices and the secondary windings and being independent, the secondary windings connected to said devices having common connection to one of the connections between the first mentioned secondary winding-autotransformer connections, switch means to th other terminals of the devices, independent means connecting the switch means to the autotransformer portion of the circuit and to the other connection between the autotransformer and the first mentioned secondary winding, the preadjusted operating current having proper phase and a value which is a multiple of the value of any portion of the autotransformer or secondary windings current values and a multiple of the supply voltage from the secondary of the input transformer to the autotransformer whereby switch means operation results in predetermined device operation.

5. A circuit, as defined by claim 4, characterized by the switch means being singular and having a common connection with the second mentioned terminals of the devices.

6. A circuit, as defined by claim 4, characterized by the switch means being of multiple charactor and having members independent of each other and individually and independently connected to a device.

'7. An alternating current supply circuit for a device operable only at a predetermined current condition and value including secondary means of an input transformer, an autotransformer connected to the secondary means, the device being interposed between the autotransformer and secondary means, and switch means in said circuit for imposing current upon the device for operation thereof, the latter current having a voltage that is a predetermined multiple of the voltage supplied by the input transformer secondary to the autotransformer.

8. An alternating current supply circuit for electrically controlled devices operable only at a predetermined voltage and phase, said circuit comprising a device of the aforesaid character, a plurality of transformer windings, each of substantially equal value, means permanently connecting certain of the transformer windings together and to th devices, and switch means operable to control the connection of the devices to at least one of the other windings for device operation only when the switch means is operated to a closed circuit position, each of the windings having a predetermined voltagephase relationship, the efiective voltage being a multiple of the supply voltage from the secondary of the input transformer to the autotransformer nd having a phase differing therefrom and each being necessary for device operation, circuit connecting means for connecting the windings in a predetermined relationship to attain that operating value of voltage and that phase relation, said switch means controlling certain of the connecting means and being connected to th devices.

9. A circuit as defined by claim 8 characterized by the circuit including a plurality of equal valued devices, and the switch means being of multiple character and arranged upon closure to effect simultaneous or predetermined selective operation of the devices.

ANDREW. B. CHRISTENSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 605,526 Steinmetz June 14, 1898 1,350,895 Th'omson Aug. 24, 1920 

